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Conversion of resistance based Adjustable Switching Power Supply to PWM based
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SiliconWizard:

--- Quote from: gnvrvikram on January 20, 2019, 09:45:35 am ---I am need of a variable DC power supply to control the voltage in the range of 0-25 V and 0-20 A. I am looking for a low cost solution.

--- End quote ---

Do you need the full current range over the full voltage range? 500W? :-DD
I would start with more humble specs if I were you. You probably don't want to burn your house down or something.

The linked module can be found everywhere on eBay, it's almost a "classic". This would be good to start a project such as what we suggested above, it's very easy to hack, but it's rated for 3A max. And you should definitely add some heatsink if you're using it at full power. But it won't get you anything near what you required above.

Paralleling DC-DC converters is usually not a good idea.

You can find 200W DC-DC converters on eBay but they are usually much more complicated than this one and will be a lot more difficult to hack especially if you don't have any schematic.
gnvrvikram:
I am looking for a microcontroller controlled Variable DC power supply that can supply me voltages in the range of 0-25 V and 0-20 A. I will not be using at full power continuously, may be for a minute or two. I need to sweep voltages from 0-25 volts repeatedly.
Zero999:
Lots of bench top power supplies have these sorts of features, but aren't cheap. You need to understand that this sort of thing will cost money.

Here are a couple of examples I found on RS Components.
https://uk.rs-online.com/web/p/bench-power-supplies/1752542/
https://docs-emea.rs-online.com/webdocs/1653/0900766b81653c32.pdf

This one is cheaper but has a USB interface and is controlled using proprietary PC software.
https://uk.rs-online.com/web/p/bench-power-supplies/7568821/
https://docs-emea.rs-online.com/webdocs/138c/0900766b8138cf36.pdf

Shop around, no doubt they can be found for less elsewhere.
gnvrvikram:
Thanks for letting me know of the available supplies. I am from India, and I could not find one that is suiting my needs or they are costly. I am looking for some solution under INR 10K.
Now I am trying with the solution with the Buck converters with low current output. Meanwhile I will try to get high current Buck converters. I shall post back once I find the solution.

Thanks and regards.
IconicPCB:
I am not sure just what INR10K buys in  India but...

Meanwell have voltage controlled switchmode supplies which will readily respond toa floating control voltage of 0 to 5Vto produce 20% to 110% variation in output.

They also have powersupplies which respond to resistance value.

The trick is to use PWM outptu from Arduino and drive an LED LDR coupler and use variation in LDR value to controlthe power supply.

LDR =light dependent resistor.

The other option is to use a PWM signal through an optocoupler and then filter to obtain DC to control the powersupply.

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